As for neural cell death and neuroprotection in the ophthalmological field, recent studies have revealed that neural cell death occurs in many diseases in optic nerve. Although a mechanism for inducing the neural cell death in diseases of optic nerve has not yet been fully elucidated, retinal ischemia is considered to be one of factors. Ischemia is defined as a lack or an insufficiency of blood circulation in tissues, and anoxemia caused by reduction of ocular blood flow due to increased intraocular pressure (IOP) is considered to play an important role in degeneration of optic nerve. On the basis of these findings, the IOP is lowered by drug therapy or surgery in current glaucoma treatment. Although its effectiveness has been proved by many studies, there are many clinical cases where IOP cannot be lowered sufficiently or those where lowering of IOP is ineffective. From a long-term viewpoint, there is a risk that patients may go blind at a considerable rate despite the therapeutic treatment. Under the circumstances, for therapeutic treatment of glaucoma, establishment of a therapeutic strategy is also desired in which direct neuroprotection for an optic nerve is seriously considered from a viewpoint of improvement of blood flow and suppression of cell death, as well as effect of lowering IOP (Exp. Eye Res. 69, 331-342 (1999) and the like).
It has been reported that a compound having hydroxy radical-scavenging action such as 3-methyl-1-phenyl-2-pyrazolin-5-one can prevent onset or progression of ocular diseases such as cataract and retinopathy (Japanese Patent Unexamined Publication (Kokai) No. Hei 7-25765). However, no report has been made on inhibitory action on neural cell death in the optic nerve.
In addition to diseases in optic nerve, each of a) retinal circulatory disorders caused by retinal vein occlusion and the like, b) retinal circulatory disorders caused by retinal artery occlusion and the like, c) retinal disorders caused by surgery, trauma and the like, d) retinal disorders caused by virus, bacteria, fungi and the like, e) macular diseases such as age-related macular degeneration, f) retinal degenerative diseases such as retinitis pigmentosa, g) retinal detachment, and h) retinal disorders caused by drugs toxic to the retina such as phenothiazine (hereinafter, these diseases will be referred to as “diseases in optic nerve and the like”) develops severe ocular function disorders, for which no appropriate therapeutic treatment is available. Therefore, an effective therapeutic medicament for these diseases is strongly desired. Accordingly, an object of the present invention is to provide a novel medicament for therapeutic treatment and/or prophylactic treatment of diseases in optic nerve and the like.